/*
 * Copyright 2016 requery.io
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package io.requery.sql;

import io.requery.query.Result;
import io.requery.query.Scalar;
import io.requery.query.BaseScalar;
import io.requery.query.Tuple;
import io.requery.query.element.QueryElement;
import io.requery.query.element.QueryOperation;

class SelectCountOperation implements QueryOperation<Scalar<Integer>> {

    private final RuntimeConfiguration configuration;
    private final TupleResultReader reader;

    SelectCountOperation(RuntimeConfiguration configuration) {
        this.configuration = configuration;
        this.reader = new TupleResultReader(configuration);
    }

    @Override
    public Scalar<Integer> evaluate(final QueryElement<Scalar<Integer>> query) {
        return new BaseScalar<Integer>(configuration.getWriteExecutor()) {
            @Override
            public Integer evaluate() {
                try (Result<Tuple> result = new SelectResult<>(configuration, query, reader)) {
                    return result.first().get(0);
                }
            }
        };
    }
}
